Breast muscle and plasma metabolomics profile of broiler chickens exposed to chronic heat stress conditions

V. S, Sekhar Mukhopadhyay C, Kashyap N, Sharma V, Singh N, Salajegheh Tazerji S, Kalantari R, Hajipour P, Singh Malik Y. Animal Wellness: The Power of Multiomics and Integrative Strategies: Multiomics in Improving Animal Health

The livestock industry faces significant challenges, with disease outbreaks being a particularly devastating issue. These diseases can disrupt the food supply chain and the livelihoods of those involved in the sector. To address this, there is a growing need to enhance the health and well-being of livestock animals, ultimately improving their performance while minimizing their environmental impact. To tackle the considerable challenge posed by disease epidemics, multiomics approaches offer an excellent opportunity for scientists, breeders, and policymakers to gain a comprehensive understanding of animal biology, pathogens, and their genetic makeup. This understanding is crucial for enhancing the health of livestock animals. Multiomic approaches, including phenomics, genomics, epigenomics, metabolomics, proteomics, transcriptomics, microbiomics, and metaproteomics, are widely employed to assess and enhance animal health. High-throughput phenotypic data collection allows for the measurement of various fitness traits, both discrete and continuous, which, when mathematically combined, define the overall health and resilience of animals, including their ability to withstand diseases. Omics methods are routinely used to identify genes involved in host-pathogen interactions, assess fitness traits, and pinpoint animals with disease resistance. Genome-wide association studies (GWAS) help identify the genetic factors associated with health status, heat stress tolerance, disease resistance, and other health-related characteristics, including the estimation of breeding value. Furthermore, the interaction between hosts and pathogens, as observed through the assessment of host gut microbiota, plays a crucial role in shaping animal health and, consequently, their performance. Integrating and analyzing various heterogeneous datasets to gain deeper insights into biological systems is a challenging task that necessitates the use of innovative tools. Initiatives like MiBiOmics, which facilitate the visualization, analysis, integration, and exploration of multiomics data, are expected to improve prediction accuracy and identify robust biomarkers linked to animal health. In this review, we discuss the details of multiomics concerning the health and well-being of livestock animals.

Effects of lycopene on the growth performance, meat quality, cecal metagenome, and hepatic untargeted metabolome in heat stressed broilers

The occurrence of heat stress in poultry houses is inevitable and leads to oxidative stress in the birds. Lycopene, a natural hydrocarbon carotenoid, possesses potent antioxidant properties. This study aimed to investigate the impact of lycopene on growth performance, meat quality, cecal microflora, and liver metabolome in broilers subjected to heat stress. A total of 480 yellow feather broilers were randomly allocated into 4 treatment groups: birds fed standard diet (Con), birds fed standard diet and supplemented with lycopene (Lyc), birds fed standard diet and subjected to heat stress (Hs), and birds fed with lycopene and subjected to heat stress (Hs-Lyc). As compared with the normal temperature groups, Hs decreased the average daily gain (ADG) of birds during d 1 to 28, lowered the pH value either in breast meat or thigh meat, increased the L* value of breast meat, and decreased the a* value of thigh meat. In comparison with non-Lyc feeding birds, Lyc supplement elevated the ADG during d 1 to 56, increased the pH of breast meat, decrease the L* and b* values of thigh meat, simultaneously increase the a* value of thigh meat. The L* of breast meat and pH of thigh meat exhibited significant differences under Hs-Lyc treatment. Lyc-treated birds exhibited higher elasticity, gumminess, and resilience in breast meat than those in non-Lyc feeding birds. The cecal metagenome analysis indicated that Hs-Lyc treatment increased the abundance of Phocaeicola salanitronis and Prevotella sp.CAG:1058, Bacteroides sp.An269, and Bacteroides sp.An19 at the species level compared with other treatments. The hepatic untargeted metabolome analysis showed that administration of Lyc upregulated 20 metabolites and downregulated 60 metabolites compared to the Con birds. Futhermore, the Hs-Lyc treatment upregulated 34 metabolites and downregulated 45 metabolites compared to the Hs birds. The correlation between the metagenome and metabolome showed that Lyc supplementation induced significant alterations in the citrate cycle, metabolism of butanoate, glycolysis/gluconeogenesis, glyoxylate and dicarboxylate, alanine, aspartate, and glutamate compared with standard supplement. In contrast, Hs-Lyc treatment induced alterations in the citrate cycle, metabolism of pyruvate, glyoxylate, and dicarboxylate, glycolysis/gluconeogenesis, arginine, proline, alanine, aspartate, and glutamate compared with the standard supplement of heat-challenged broilers. In summary, dietary Lyc supplementation promoted the growth performance, changed the meat quality, modulated the cecal metagenome and hepatic metabolome in heat-stressed broilers.

Partial substitution of soybean meal with microalgae meal (Arthrospira spp. - Spirulina) in grower and finisher diets for broiler chickens: implications on performance parameters, footpad dermatitis occurrence, breast meat quality traits, amino acid digestibility and plasma metabolomics profile

This trial was conducted to evaluate the effects of replacing soybean meal with microalgae meal (MM; Arthrospira spp.) during grower and finisher phases on productive performance, footpad dermatitis (FPD) occurrence, breast meat quality, amino acid digestibility and plasma metabolomics profile of broiler chickens. One thousand day-old Ross 308 male chicks were divided into 5 experimental groups (8 replicates, 25 birds/each): CON, fed a commercial soybean-based diet throughout the trial (0-41 d); F3 and F6, fed the CON diet up to 28 d of age and then a finisher diet (29-41 d) with either 30 or 60 g MM/kg, respectively; and GF3 and GF6, receiving CON diet until 14 d and then diets containing 30 or 60 g MM/kg from 15 to 41 d, respectively. All diets were iso-energetic and with a similar amino acid profile. Growth performances were recorded on a pen basis at the end of each feeding phase and apparent ileal amino acid digestibility was determined at 41 d. Footpad dermatitis occurrence was assessed on all processed birds, while breast and plasma samples were collected for meat quality and metabolomics analysis (proton nuclear magnetic resonance - 1H-NMR). At 41 d, CON group showed higher body weight than F6 and GF6 ones (2,541 vs. 2,412 vs. 2,384 g, respectively; P < 0.05). Overall, GF6 group exhibited the highest feed conversion ratio, while F3 did not present significant differences compared to CON (1.785 vs. 1.810 vs. 1.934 g feed/g gain, respectively for CON, F3 and GF6; P < 0.01). The occurrence and the risk of developing FPD were similar among groups. MM administration increased breast meat yellowness and reduced amino acid digestibility (P < 0.001). The 1H-NMR analysis revealed variations in the levels of some circulating metabolites, including histidine, arginine and creatine, which play important metabolic roles. Overall, these findings can contribute to expand the knowledge about the use of Arthrospira spp. as protein source in broiler diets.

Dietary supplementation with Chlorella vulgaris in broiler chickens submitted to heat-stress: effects on growth performance and meat quality

Heat stress can greatly challenge growth and meat quality of broiler chickens where research is looking for sustainable ingredients, such as microalgae, that could also alleviate its negative impacts. Thus, in the present study, 576 1-D-old chicks (Ross 308) were housed until commercial slaughtering (42 D) in 36 pens in 2 rooms of a poultry house, according to a full factorial design encompassing 2 room temperatures (standard vs. high), 2 sexes (females vs. males), and 3 dietary treatments, that is, diet C0 (control diet), diet C3, and diet C6 containing 0, 3, and 6%, respectively, of C. vulgaris meal replacing the same quantities of soybean meal. The highest inclusion level of C. vulgaris decreased feed intake (P < 0.001) and body weight (P < 0.0001) compared to the control diet; it increased yellow and red indexes (P < 0.0001) of the breast muscle, besides the proportion of n3 polyunsaturated fatty acids (PUFA) (P = 0.028). Heat stress decreased feed intake (P = 0.001), breast (P = 0.001) and p. major yields (P = 0.036), and increased meat pH (P= 0.008) and cooking losses (P < 0.001), umami (P = 0.021) and brothy flavor (P < 0.001), and the proportion of n3 PUFA rates (P = 0.027), while reducing the contents of several amino acids in the breast meat (P ≤ 0.05). Compared to females, males displayed higher feed intake and growth, and more favorable feed conversion (P < 0.001). Carcass and p. major yields were greater in females (P < 0.001) which also showed a higher occurrence of spaghetti meat compared to males (P < 0.001). In conclusion, C. vulgaris can be used to replace until 3% of soybean meal in diets for broiler chickens without negative implications, while positively affecting breast meat color according to consumers' preferences. However, the microalgae inclusion did not mitigate the negative effects of a chronic heat stress on growth performance nor reduced the occurrence of any myopathies.

Effect of an immune challenge and two feed supplements on broiler chicken individual breast muscle protein synthesis rate

Optimization of broiler chicken breast muscle protein accretion is key for the efficient production of poultry meat, whose demand is steadily increasing. In a context where antimicrobial growth promoters use is being restricted, it is important to find alternatives as well as to characterize the effect of immunological stress on broiler chicken's growth. Despite its importance, research on broiler chicken muscle protein dynamics has mostly been limited to the study of mixed protein turnover. The present study aims to characterize the effect of a bacterial challenge and the feed supplementation of citrus and cucumber extracts on broiler chicken individual breast muscle proteins fractional synthesis rates (FSR) using a recently developed dynamic proteomics pipeline. Twenty-one day-old broiler chickens were administered a single 2H2O dose before being culled at different timepoints. A total of 60 breast muscle protein extracts from five experimental groups (Unchallenged, Challenged, Control Diet, Diet 1 and Diet 2) were analysed using a DDA proteomics approach. Proteomics data was filtered in order to reliably calculate multiple proteins FSR making use of a newly developed bioinformatics pipeline. Broiler breast muscle proteins FSR uniformly decreased following a bacterial challenge, this change was judged significant for 15 individual proteins, the two major functional clusters identified as well as for mixed breast muscle protein. Citrus or cucumber extract feed supplementation did not show any effect on the breast muscle protein FSR of immunologically challenged broilers. The present study has identified potential predictive markers of breast muscle growth and provided new information on broiler chicken breast muscle protein synthesis which could be essential for improving the efficiency of broiler chicken meat production. SIGNIFICANCE: The present study constitutes the first dynamic proteomics study conducted in a farm animal species which has characterized FSR in a large number of proteins, establishing a precedent for biomarker discovery and assessment of health and growth status. Moreover, it has been evidenced that the decrease in broiler chicken breast muscle protein following an immune challenge is a coordinated event which seems to be the main cause of the decreased growth observed in these animals.

Strategies to combat heat stress in poultry production-A review

The effects of heat stress (HS) caused by high temperatures continue to be a global concern in poultry production. Poultry birds are homoeothermic, however, modern-day chickens are highly susceptible to HS due to their inefficiency in dissipating heat from their body due to the lack of sweat glands. During HS, the heat load is higher than the chickens' ability to regulate it. This can disturb normal physiological functioning, affect metabolism and cause behavioural changes, respiratory alkalosis and immune dysregulation in birds. These adverse effects cause gut dysbiosis and, therefore, reduce nutrient absorption and energy metabolism. This consequently reduces production performances and causes economic losses. Several strategies have been explored to combat the effects of HS. These include environmentally controlled houses, provision of clean cold water, low stocking density, supplementation of appropriate feed additives, dual and restricted feeding regimes, early heat conditioning and genetic selection of poultry lines to produce heat-resistant birds. Despite all these efforts, HS still remains a challenge in the poultry sector. Therefore, there is a need to explore effective strategies to address this long-lasting problem. The most recent strategy to ameliorate HS in poultry is early perinatal programming using the in ovo technology. Such an approach seems particularly justified in broilers because chick embryo development (21 days) equals half of the chickens' posthatch lifespan (42 days). As such, this strategy is expected to be more efficient and cost-effective to mitigate the effects of HS on poultry and improve the performance and health of birds. Therefore, this review discusses the impact of HS on poultry, the advantages and limitations of the different strategies. Finally recommend a promising strategy that could be efficient in ameliorating the adverse effects of HS in poultry.

Metabolomics analysis to interpret changes in physiological and metabolic responses to chronic heat stress in Pekin ducks

Heat stress (HS) is a major environmental threat that affects duck production in subtropical and tropical regions, especially in summer. This study aimed to evaluate the physiological and metabolic responses of Pekin ducks to chronic HS conditions via liquid chromatography-mass spectrometry (LC-MS) using a paired-fed (PF) experimental design. On the basis of equivalent feed intake (HS vs. PF), HS significantly reduced growth performance and the percentage of leg and breast muscles, however, markedly increased the percentage of abdominal fat and breast skin fat. Serum metabolomics results revealed that heat-stressed ducks showed enhanced glycolysis and pentose phosphate pathways, as demonstrated by higher glucose 6-phosphate and 6-phogluconic acid levels in the PF vs. HS comparison. HS decreased hepatic mRNA levels of mitochondrial fatty acid β-oxidation-related genes (MCAD and SCAD) compared to the PF group, resulting in acetylcarnitine accumulation in serum. Moreover, HS elevated the concentrations of serum amino acids and mRNA levels of ubiquitination-related genes (MuRF1 and MAFbx) in the skeletal muscle and amino acid transporter-related genes (SLC1A1 and SLC7A1) and gluconeogenesis-related genes (PCK1 and PCase) in the liver compared to the PF group. When compared to the normal control group (NC), HS further decreased growth performance, but it elevated the abdominal fat rate. However, increased mRNA levels of ubiquitination-related genes and serum amino acid accumulation were not observed in the HS group compared to the NC group, implying that reduced feed intake masked the effect of HS on skeletal muscle breakdown and is a form of protection for the organism. These results suggest that chronic HS induces protein degradation in the skeletal muscle to provide amino acids for hepatic gluconeogenesis to provide sufficient energy, as Pekin ducks under HS conditions failed to efficiently oxidise fatty acids and ketones in the mitochondria, leading to poor growth performance and slaughter characteristics.

Effects of Heat Stress on Breast Muscle Metabolomics and Lipid Metabolism Related Genes in Growing Broilers

With global warming and worsening climatic conditions, heat stress (HS) has become a significant challenge affecting the development of poultry production. In this study, we aimed to determine the effects of HS on breast muscle metabolomics and lipid metabolism-related genes in growing broilers. One hundred twenty 29-day-old Arbor Acres broilers were randomly divided into normal temperature (NT; 21 ± 1 °C) and heat stress (HS; 31 ± 1 °C) groups, with six replicates (ten birds in each replicate) in each group, raised for 14 days in two environment chambers at 60 ± 7% relative humidity. Compared with the broilers in the NT group, the average daily food intake, average daily gain and breast muscle yield in the HS group were significantly lower (p < 0.05). The feed conversion ratio was significantly higher in the HS group (p < 0.05). The concentrations of serum corticosterone, free fatty acids and cholesterol and the percentage of abdominal fat of broilers in the HS group were significantly higher (p < 0.05) than the values of the broilers in the NT group. Untargeted breast muscle metabolome analysis revealed 14 upregulated differential metabolites, including glycerophosphocholine, and 27 downregulated differential metabolites, including taurine, in the HS group compared to the NT group; the HS group also displayed significant effects on six metabolic pathways compared to the NT group (p < 0.05). The mRNA expression levels of peroxisome proliferator-activated receptor gamma coactivator-1-alpha, peroxisome proliferator-activated receptor alpha (PPARα) and ATP-binding cassette transporter A1 in the liver and breast muscles were significantly decreased in the HS group compared with the NT group (p < 0.05). The collective findings reveal that HS can cause disorders in breast muscle lipid metabolism in broilers. The PPARα gene might be the key gene in the mechanism of the lipid metabolism that is induced by HS in breast muscle of broilers. These findings provide novel insights into the effects of HS on chicken growth.

Effect of chronic heat stress on the carbonylation of glycolytic enzymes in breast muscle and its correlation with the growth performance of broilers

Chronic heat stress has detrimental effects on the growth performance of broilers, and the potential mechanism is under exploration. In this study, the protein carbonyl modification was introduced to glycolytic enzymes to evaluate its relationship with the growth performance of heat-stressed (HS) broilers. A total of 144 male 28-day-old broilers were assigned to 3 treatments: the normal control group (NC, raised at 22°C with free access to feed and water), the HS group (raised at 32°C with free access to feed and water), and the pair-fed group (PF, raised at 22°C with an amount of feed equal to that consumed by the HS group on a previous day). Results showed that heat stress decreased the average daily growth, increased the feed-to-gain ratio (F/G), decreased breast muscle rate, and increased abdominal fat rate compared with the NC and PF groups (P < 0.05). Higher cloacal temperature and serum creatine kinase activity were found in the HS group than those of the NC and PF groups (P < 0.05). Heat stress increased the contents of carbonyl, advanced glycation end-products, malonaldehyde, and the activities of catalase, glutathione peroxidase, and total antioxidant capacity compared with the NC and PF groups (P < 0.05). Heat stress increased the contents of glucose and lactate, declined the glycogen content, and lowered the relative protein expressions of pyruvate kinase muscle type, lactate dehydrogenase A type (LDHA), and citrate synthase compared to those of the NC group (P < 0.05). In contrast to the NC and PF groups, heat stress intensified the carbonylation levels of phosphoglucomutase 1, triosephosphate isomerase 1, β-enolase, and LDHA, which were positively correlated with the F/G (P < 0.05). These findings demonstrate that heat stress depresses growth performance on account of oxidative stress and glycolysis disorders. It further increases the carbonylation of glycolytic enzymes, which potentially correlates with the F/G by disturbing the mode of energy supply of broilers.

A Technical Report on the Potential Effects of Heat Stress on Antioxidant Enzymes Activities, Performance and Small Intestinal Morphology in Broiler Chickens Administered Probiotic and Ascorbic Acid during the Hot Summer Season

Oxidative stress negatively affects the welfare of broiler chickens leading to poor productivity and even death. This study examined the negative effect of heat stress on antioxidant enzyme activities, small intestinal morphology and performance in broiler chickens administered probiotic and ascorbic acid during the hot summer season, under otherwise controlled conditions. The study made use of 56 broiler chickens; which were divided into control; probiotic (1 g/kg); ascorbic acid (200 mg/kg) and probiotic + ascorbic acid (1 g/kg and 200 mg/kg, respectively). All administrations were given via feed from D1 to D35 of this study. Superoxide dismutase, glutathione peroxidase and catalase activities were highly significant (p < 0.0001) in the treatment groups compared to the control. Performance indicators (water intake and body weight gain) were significantly higher (p < 0.05) in the probiotic and probiotic + ascorbic acid group. The height of duodenal, jejunal and ileal villi, and goblet cell counts of broiler chickens were significantly different in the treatment groups. In conclusion, the study showed that heat stress negatively affects the levels of endogenous antioxidant enzymes, performance and the morphology of small intestinal epithelium, while the antioxidants were efficacious in ameliorating these adverse effects.

Resiliency of fast-growing and slow-growing genotypes of broiler chickens submitted to different environmental temperatures: growth performance and meat quality

Growth performance and meat quality were assessed in 238 chicks of both sexes belonging to a commercial crossbreed (Ross 308), and 2 Italian local breeds (Bionda Piemontese-BP and Robusta Maculata-RM). The chickens were kept in 2 rooms at standard environmental conditions or under heat stress (+4.7°C on average) until slaughtering (42 d of age for Ross 308 and 99 d for RM and BP chickens). The Ross chickens showed the highest final live weight, feed intake, and daily weight gain, and the best feed conversion ratio compared to the local breeds (P < 0.001), with RM performing better than BP chickens. Thus, Ross chickens had the heaviest carcasses, the highest slaughter, and breast yields followed by RM and BP chickens (P < 0.001). At the pectoralis major (p. major) muscle, Ross chickens showed the highest pH, lightness, and yellowness, besides the highest cooking losses, whereas BP showed the highest redness (P < 0.001). Ross meat had higher water and ether extract contents, and lower crude protein content compared to BP and RM (P < 0.001), whereas no differences among genotypes were measured for the fatty acid profile. At the sensory analysis, Ross breasts had a higher juiciness compared to BP ones, besides a lower score for "brothy and chickeny/meaty" and a higher one for "wet feathers" compared to local breeds (0.05 < P < 0.001). The increase of the room temperature decreased growth performance and cold carcass weight (P < 0.001) compared to standard conditions, whereas the rate of α-linolenic acid in the meat increased (P < 0.01). The effect of a high environmental temperature on growth performance and slaughter and meat quality traits was more pronounced in Ross compared to BP and RM chickens (0.05 < P <0.001; significant interaction genotype × temperature). In conclusions, local chicken breeds showed lower performance and slaughter yield compared to the commercial genotype, but more favorable meat quality traits and higher resilience to the environmental heat-stress.

Heat hardening enhances metabolite-driven thermoprotection in the Mediterranean mussel Mytilus galloprovincialis

Introduction: Temperature affects organisms' metabolism and ecological performance. Owing to climate change, sea warming constituting a severe source of environmental stress for marine organisms, since it increases at alarming rates. Rapid warming can exceed resilience of marine organisms leading to fitness loss and mortality. However, organisms can improve their thermal tolerance when briefly exposed to sublethal thermal stress (heat hardening), thus generating heat tolerant phenotypes. Methods: We investigated the "stress memory" effect caused by heat hardening on M. galloprovincialis metabolite profile of in order to identify the underlying biochemical mechanisms, which enhance mussels' thermal tolerance. Results: The heat hardening led to accumulation of amino acids (e.g., leucine, isoleucine and valine), including osmolytes and cytoprotective agents with antioxidant and anti-inflammatory properties that can contribute to thermal protection of the mussels. Moreover, proteolysis was inhibited and protein turnover regulated by the heat hardening. Heat stress alters the metabolic profile of heat stressed mussels, benefiting the heat-hardened individuals in increasing their heat tolerance compared to the non-heat-hardened ones. Discussion: These findings provide new insights in the metabolic mechanisms that may reinforce mussels' tolerance against thermal stress providing both natural protection and potential manipulative tools (e.g., in aquaculture) against the devastating climate change effects on marine organisms.

Heat stress exposure cause alterations in intestinal microbiota, transcriptome, and metabolome of broilers

Introduction

Heat stress can affect the production of poultry through complex interactions between genes, metabolites and microorganisms. At present, it is unclear how heat stress affects genetic, metabolic and microbial changes in poultry, as well as the complex interactions between them.

Methods

Thus, at 28  days of age a total of 200 Arbor Acres broilers with similar body weights were randomly divided into the control (CON) and heat stress treatment (HS). There were 5 replicates in CON and HS, respectively, 20 per replication. From the 28-42  days, the HS was kept at 31 ± 1°C (9:00-17:00, 8 h) and other time was maintained at 21 ± 1°C as in the CON. At the 42nd day experiment, we calculated the growth performance (n = 8) of broilers and collected 3 and 6 cecal tissues for transcriptomic and metabolomic investigation and 4 cecal contents for metagenomic investigation of each treatment.

Results and discussion

The results indicate that heat stress significantly reduced the average daily gain and body weight of broilers (value of p < 0.05). Transcriptome KEGG enrichment showed that the differential genes were mainly enriched in the NF-kB signaling pathway. Metabolomics results showed that KEGG enrichment showed that the differential metabolites were mainly enriched in the mTOR signaling pathway. 16S rDNA amplicon sequencing results indicated that heat stress increased the relative abundance of Proteobacteria decreased the relative abundance of Firmicutes. Multi-omics analysis showed that the co-participating pathway of differential genes, metabolites and microorganisms KEGG enrichment was purine metabolism. Pearson correlation analysis found that ornithine was positively correlated with SULT1C3, GSTT1L and g_Lactobacillus, and negatively correlated with CALB1. PE was negatively correlated with CALB1 and CHAC1, and positively with g_Alistipes. In conclusion, heat stress can generate large amounts of reactive oxygen and increase the types of harmful bacteria, reduce intestinal nutrient absorption and antioxidant capacity, and thereby damage intestinal health and immune function, and reduce growth performance indicators. This biological process is manifested in the complex regulation, providing a foundational theoretical basis for solving the problem of heat stress.

Impact of chronic heat stress on behavior, oxidative status and meat quality traits of fast-growing broiler chickens

This research aimed to investigate, through a multifactorial approach, the relationship among some in-vivo parameters (i.e., behavior and blood traits) in broilers exposed to chronic HS, and their implications on proximate composition, technological properties, and oxidative stability of breast meat. A total of 300 Ross 308 male chickens were exposed, from 35 to 41 days of age, to either thermoneutral conditions (TNT group: 20°C; six replicates of 25 birds/each) or elevated ambient temperature (HS group: 24 h/d at 30°C; six replicates of 25 birds/each). In order to deal with thermal stress, HS chickens firstly varied the frequency of some behaviors that are normally expressed also in physiological conditions (i.e., increasing "drinking" and decreasing "feeding") and then exhibited a behavioral pattern finalized at dissipating heat, primarily represented by "roosting," "panting" and "elevating wings." Such modifications become evident when the temperature reached 25°C, while the behavioral frequencies tended to stabilize at 27°C with no further substantial changes over the 6 days of thermal challenge. The multifactorial approach highlighted that these behavioral changes were associated with oxidative and inflammatory status as indicated by lower blood γ-tocopherol and higher carbonyls level (0.38 vs. 0.18 nmol/mL, and 2.39 vs. 7.19 nmol/mg proteins, respectively for TNT and HS; p < 0.001). HS affected breast meat quality by reducing the moisture:protein ratio (3.17 vs. 3.01, respectively for TNT and HS; p < 0.05) as well as the muscular acidification (ultimate pH = 5.81 vs. 6.00, respectively; p < 0.01), resulting in meat with higher holding capacity and tenderness. HS conditions reduced thiobarbituric acid reactive substances (TBARS) concentration in the breast meat while increased protein oxidation. Overall results evidenced a dynamic response of broiler chickens to HS exposure that induced behavioral and physiological modifications strictly linked to alterations of blood parameters and meat quality characteristics.

1H nuclear magnetic resonance-based metabolomics study of serum and pectoralis major for different commercial chicken breeds

This study aimed to characterize the metabolic composition of four types of commercially available chicken breeds [village chicken, colored broiler (Hubbard), broiler (Cobb), and spent layers (Dekalb)] by 1H NMR coupling and discriminate them using multivariate analysis. Five chickens were collected for each chicken breed based on the marketing age from the respective commercial farms. The orthogonal partial least squares discriminant analysis (OPLS-DA) results showed an obvious separation of local village chickens from the other breeds based on the metabolites present in their serum and meat (pectoralis major). The cumulative values of Q 2, R 2 X, and R 2 Y of the OPLS-DA model for chicken serum were 0.722, 0.877, and 0.841. For the pectoralis major muscle, the cumulative values of Q 2, R 2 X, and R 2 Y of the OPLS-DA model were reported as 0.684, 0.781, and 0.786, respectively. The quality of both OPLS-DA models was accepted by the cumulative values of Q 2 ≥ 0.5 and R 2 ≥ 0.65. The 1H NMR result with multivariate analysis has successfully distinguished local village chicken from the other three commercial chicken breeds based on serum and pectoralis major muscle. Nonetheless, colored broiler (Hubbard) was not distinguished from broiler (Cobb) and spent layers (Dekalb) in serum and pectoralis major, respectively. The OPLS-DA assessment in this study identified 19 and 15 potential metabolites for discriminating different chicken breeds in serum and pectoralis major muscle, respectively. Some of the prominent metabolites identified include amino acids (betaine, glycine, glutamine, guanidoacetate, phenylalanine, and valine), nucleotides (IMP and NAD+), organic acids (lactate, malate, and succinate), peptide (anserine), and sugar alcohol (myo-inositol).

Metabolic and microbiota response to arginine supplementation and cyclic heat stress in broiler chickens

Little attention has been paid to the biological role of arginine and its dietary supplementation in broilers under heat stress (HS) conditions. Therefore, the main aim of this study was to assess the response of broilers to arginine supplementation and cyclic HS, with a focus on liver, pectoral muscle, and blood metabolic profiles and the cecal microbiota. Day-old male Ross 308 broilers (n = 240) were placed in 2 rooms with 12 pens each for a 44-day trial. Pens were assigned to one of two groups (6 pens/group/room): the control group (CON) was given a basal diet in mash form and the treated group (ARG) was fed CON diet supplemented with crystalline L-arginine. The total arginine:lysine ratio of CON diet ranged between 1.02 and 1.07, while that of ARG diet was 1.20. One room was constantly kept at thermoneutral (TN) conditions, while the birds in the other room were kept at TN conditions until D34 and subjected to cyclic HS from D35 onwards (∼34°C; 9:00 A.M.–6:00 P.M.). Blood, liver, Pectoralis major muscle, and cecal content were taken from 2 birds per pen (12 birds/group/room) for metabolomics and microbiota analysis. Growth performance data were also collected on a pen basis. Arginine supplementation failed to reduce the adverse effects of HS on growth performance. Supplemented birds showed increased levels of arginine and creatine in plasma, liver, and P. major and methionine in liver, and reduced levels of glutamine in plasma, liver, and P. major. HS altered bioenergetic processes (increased levels of AMP and reduced levels of fumarate, succinate, and UDP), protein metabolism (increased protein breakdown to supply the liver with amino acids for energy production), and promoted the accumulation of antioxidant and protective molecules (histidine-containing dipeptides, beta-alanine, and choline), especially in P. major. Arginine supplementation may have partially counterbalanced the effects of HS on energy homeostasis by increasing creatine levels and attenuating the increase in AMP levels, particularly in P. major. It also significantly reduced cecal observed diversity, while HS increased alpha diversity indices and affected beta diversity. Results of taxonomic analysis at the phylum and family level are also provided.

Dietary L-citrulline modulates the growth performance, amino acid profile, and the growth hormone/insulin-like growth factor axis in broilers exposed to high temperature

Heat stress adversely affects the growth performance, muscle development, and protein metabolism in poultry. l-Citrulline (L-Cit), is a non-essential amino acid that is known to stimulate muscle protein synthesis under stress conditions. This study investigated whether L-Cit could influence the growth performance, amino acid profile, and protein metabolism in broilers exposed to high ambient temperature. In a 2 × 2 factorial arrangement, Arbor acre broilers (288 chickens) were fed with basal diet (CON) or 1% L-Cit supplemented diet and later subjected to either thermoneutral (TNZ: 24°C, 24 h/d) or heat stress (HS: 35°C for 8 h/d) environment for 21 days. The results showed that L-Cit diet promoted the body weight and body weight gain of broilers higher than the CON diet, and it further alleviated HS suppression of body weight and feed intake at certain periods (p < 0.05). Plasma urea, uric acid, glucose, and total cholesterol were elevated during HS, whereas, the triglyceride content was decreased (p < 0.05). Serum amino acids including citrulline, alanine, aspartate, and taurine were decreased by HS. L-Cit supplementation restored the citrulline level and alleviated HS induction of 3-methylhistidine (p < 0.05). L-Cit supplementation increased the plasma growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentration, as well as the GH concentration in the breast muscle (p < 0.05). The mRNA expression showed that HS elicited tissue-specific responses by upregulating some growth factors in the breast muscle, but downregulated the GH receptor, GH binding protein, and IGF-1 expression in the hypothalamus. L-Cit supplementation upregulated the GHRH and IGFBP2 expression in the hypothalamus. L-Cit also upregulated the expression of IGF-1R and IGFBP2 in the breast muscle of HS broilers. The total mTOR protein level in the breast muscle of HS broilers was also increased by L-Cit diet (p < 0.05). Therefore, this study demonstrated that HS negatively affected the growth performance of broilers and dysregulated the expression of growth factors related to protein metabolism. Contrarily, L-Cit promoted the growth responses of broilers via its stimulation of circulating GH/IGF-1 concentration. To certain extents, L-Cit supplementation elicited protective effects on the growth performance of HS broilers by diminishing protein catabolism.

A review of heat stress in chickens. Part I: Insights into physiology and gut health

Heat stress (HS) compromises the yield and quality of poultry products and endangers the sustainability of the poultry industry. Despite being homeothermic, chickens, especially fast-growing broiler lines, are particularly sensitive to HS due to the phylogenetic absence of sweat glands, along with the artificial selection-caused increase in metabolic rates and limited development of cardiovascular and respiratory systems. Clinical signs and consequences of HS are multifaceted and include alterations in behavior (e.g., lethargy, decreased feed intake, and panting), metabolism (e.g., catabolic state, fat accumulation, and reduced skeletal muscle accretion), general homeostasis (e.g., alkalosis, hormonal imbalance, immunodeficiency, inflammation, and oxidative stress), and gastrointestinal tract function (e.g., digestive and absorptive disorders, enteritis, paracellular barrier failure, and dysbiosis). Poultry scientists and companies have made great efforts to develop effective solutions to counteract the detrimental effects of HS on health and performance of chickens. Feeding and nutrition have been shown to play a key role in combating HS in chicken husbandry. Nutritional strategies that enhance protein and energy utilization as well as dietary interventions intended to restore intestinal eubiosis are of increasing interest because of the marked effects of HS on feed intake, nutrient metabolism, and gut health. Hence, the present review series, divided into Part I and Part II, seeks to synthesize information on the effects of HS on physiology, gut health, and performance of chickens, with emphasis on potential solutions adopted in broiler chicken nutrition to alleviate these effects. Part I provides introductory knowledge on HS physiology to make good use of the nutritional themes covered by Part II.

Effect of chronic heat stress on gastrointestinal histology and expression of feed intake-regulatory hormones in broiler chickens

Heat stress (HS) dramatically impairs the growth performance of broiler chickens, mainly as a consequence of reduced feed intake due to the loss of appetite. This study was aimed at evaluating the alterations induced by chronic HS conditions on the morphological and morphometric features of the gastrointestinal (GI) tract and on the expression of some enteroendocrine cells (EECs) involved in the regulation of feed intake in chickens. Three hundred male chickens (Ross 308) were divided into two experimental groups and raised either in thermoneutral environment for the whole fattening period (0-41 days) (TNT group) or subjected to chronic HS conditions (30 °C for 24 h/day) from 35 to 41 days (HS group). Samples of proventriculus, duodenum, jejunum and cecum were collected from 24 broilers (12/group). Haematoxylin-eosin was used for the morphometric evaluations, while immunohistochemistry was applied for the evaluation of EECs expressing ghrelin (GHR), cholecystokinin (CCK), neuropeptide Y (NPY), glucagon-like peptide-1 (GLP-1), and serotonin (5-HT). In the proventriculus, HS reduced total wall thickness and mucous layer height (P ≤ 0.01) as well as mean diameter, circumference, and area of the compound tubular glands (P ≤ 0.001) with respect to TNT. The small intestine of HS birds was characterised by decreased villous height and total thickness (duodenum, P ≤ 0.01; jejunum, P ≤ 0.001), whereas crypt depth and width were reduced only in the jejunum (P ≤ 0.01). HS had negligible effects on the morphological aspects of the cecum. In the proventriculus, an increase in GHR and NPY EECs was observed in response to HS (P ≤ 0.001). Similarly, the small intestine villi of the HS group showed greater GLP-1 (P ≤ 0.05), 5-HT (P ≤ 0.001) and CCK (P ≤ 0.01) EECs. Moreover, the expression of 5-HT EECs was higher in the duodenal (P ≤ 0.01) and jejunal (P ≤ 0.01) crypts of HS birds, whereas GLP-1 and CCK EECs increased only in jejunal crypts (P ≤ 0.05). Finally, 5-HT EEC expression was increased in the cecum of HS group (P ≤ 0.01). In conclusion, these outcomes demonstrate that chronic HS induces morphometric alterations not only in the small intestine but also in a key organ such as the proventriculus. Furthermore, HS conditions affect the presence and distribution of EECs, suggesting that some GI peptides and biogenic amine may be implicated in the regulation of appetite and voluntary feed intake in heat-stressed broiler chickens.

Omics technologies in poultry health and productivity - part 1: current use in poultry research

In biology, molecular terms with the suffix "-omics" refer to disciplines aiming at the collective characterization of pools of molecules derived from different layers (DNA, RNA, proteins, metabolites) of living organisms using high-throughput technologies. Such omics analyses have been widely implemented in poultry research in recent years. This first part of a bipartite review on omics technologies in poultry health and productivity examines the use of multiple omics and multi-omics techniques in poultry research. More specific present and future applications of omics technologies, not only for the identification of specific diagnostic biomarkers, but also for potential future integration in the daily monitoring of poultry production, are discussed in part 2. Approaches based on omics technologies are particularly used in poultry research in the hunt for genetic markers of economically important phenotypical traits in the host, and in the identification of key bacterial species or functions in the intestinal microbiome. Integrative multi-omics analyses, however, are still scarce. Host physiology is investigated via genomics together with transcriptomics, proteomics and metabolomics techniques, to understand more accurately complex production traits such as disease resistance and fertility. The gut microbiota, as a key player in chicken productivity and health, is also a main subject of such studies, investigating the association between its composition (16S rRNA gene sequencing) or function (metagenomics, metatranscriptomics, metaproteomics, metabolomics) and host phenotypes. Applications of these technologies in the study of other host-associated microbiota and other host characteristics are still in their infancy.

Meta-Analysis and Systematic Review of the Thermal Stress Response: Gallus gallus domesticus Show Low Immune Responses During Heat Stress

Heat stress, which affects broiler growth performance and immunity, is a major concern in the poultry industry. This meta-analysis aimed to demonstrate the significant effect of heat stress on broiler mass gain and immunoglobulin levels, which regulates the mortality rate of broilers. A total of 2,585 studies were downloaded from PubMed, Web of Science, and Google Scholar from January 1, 2015, to September 1, 2021. Eventually, 28 studies were selected based on specific criteria. The results for body mass gain, total mass of immune organs (thymus, spleen, and bursa of Fabricius), immunoglobulin (IgA, IgG, and IgM) levels, and mortality rate were analyzed using odds ratio or the random-effects model (REM) at a confidence interval (CI) of 95%. Compared to the control, heat stress significantly decreased body mass gain (10 trials: REM = 1.35, 95% CI: 1.21, 1.50). Compared to that in the control, heat stress significantly increased immunoglobulin levels: IgA (7 trials: REM = 1.69, 95% CI: 0.90, 3.16), IgG (6 trials: REM = 1.24, 95% CI: 0.85, 1.81), IgM (8 trials: REM = 0.69, 95% CI: 0.44, 1.08), and heat stress also increased the broiler mortality rate (6 trials: REM = 0.06, 95% CI: 0.01, 0.27). However, there were no significant changes in the immune organs between the control and heat-stressed groups. In conclusion, heat stress remarkably alters the mass gain and immunoglobulin levels of broilers, which may be a cause of the high mortality rate.

How the kinetic behavior of organic chickens affects productive performance and blood and meat oxidative status: a study of six poultry genotypes

The aim of this study was to analyze the relationship between the kinetic behavior, carcass characteristics, oxidative status (blood and meat), and meat fatty acid profiles of 6 organically reared slower growing chicken genotypes (SrG). One hundred male chickens of 6 SrG were used: Ranger Classic (RC), Ranger Gold (RG), Rowan Ranger (RR), RedJA (RJ), CY Gen 5 JA87 (CY), and M22 × JA87 (M). Twenty chickens/genotype were selected to analyze behavior, while, 15 individuals were slaughtered and different traits were analyzed in the blood and drumstick meat. The variables were grouped into different principal components: kinetic activity (PC1, with explorative attitude as the highest score), productive performance (PC2, carcass and head/feet yields), blood (PC3, carbonyls, and TBARS) and meat (PC6, thiols, and TBARS) markers, technological traits (PC4, pH, and color), proximate meat composition (PCA5, moisture, lipids, protein, and ash), fatty acid profile, and nutritional indexes (PC7, IP, and PUFAn-3). Uni- and bivariate analyses showed a strong positive association between kinetic behaviors and blood and meat oxidation and a medium positive association with fatty acid profile and nutritional indexes, whereas a negative association was found between productive performance loads and the technological traits of meat. Generalized linear models showed that all PCs were influenced by genotype. In particular, CY and M resulted as less active genotypes; conversely, RR showed more kinetic activity, whereas RJ, RG, and RC exhibited intermediate levels of activity. Cluster analysis of kinetic behavior and blood or meat oxidative status highlighted 2 groups: nonwalking (NW: CY and M) and walking (W: RC, RG, RR, and RJ) animals. However, in the W group, another was visualized, constituted by genotypes with high kinetic activity resulting in the worst oxidative balance (Walking not trained-genotypes, Wnt: RR and RJ). The present results confirmed that the kinetic behavior of SrG genotypes is negatively correlated with productive performance. Furthermore, a significant association between kinetic behavior and blood (positively correlated) or meat (negatively correlated) oxidative status was noted. Such differences are mainly due to the intrinsic response of the genotypes used (i.e., training-walking capacity).